Pollution in eastern China cuts rainfall

Increased amounts of air pollution in China over last 50 years reduces days of rain by up to a quarter

RICHLAND, Wash. – New research shows that air pollution in eastern China has reduced the amount of light rainfall over the past 50 years and decreased by 23 percent the number of days of light rain in the eastern half of the country. The results suggest that bad air quality might be affecting the country’s ability to raise crops as well as contributing to health and environmental problems. The study links for the first time high levels of pollutants in the air with conditions that prevent the light kind of rainfall critical for agriculture. Led by atmospheric scientist Yun Qian at the Department of Energy’s Pacific Northwest National Laboratory, the study appears August 15 in the Journal of Geophysical Research-Atmospheres. “People have long wondered if there was a connection, but this is the first time we’ve observed it from long-term data,” said Qian. “Besides the health effects, acid rain and other problems that pollution creates, this work suggests that reducing air pollution might help ease the drought in north China.” China’s dramatic economic growth and pollution problems provide researchers an opportunity to study the connection between air quality and climate. Rain in eastern China — where most of the country’s people and pollution exist — is not like it used to be. Over the last 50 years, the southern part of eastern China has seen increased amounts of total rainfall per year. The northern half has seen less rain and more droughts. But light rainfall that sustains crops has decreased everywhere. A group of climate researchers from the U.S., China and Sweden wanted to know why light rain patterns haven’t followed the same precipitation patterns as total rainfall. Previous work has shown that pollution can interfere with light rain above oceans, so the team suspected pollution might have something to do with the changes over land. Light rain ranges from drizzles to 10 millimeters of accumulation per day and sustains agriculture. (Compared to heavy rain that causes floods, loss of light rain has serious consequences for crops.) While the light rains have diminished, pollution has increased dramatically in China in the last half of the 20th century. For example, while China’s population rose two and a half times in size, the emissions of sulfur from fossil fuel burning outpaced that considerably — rising nine times. …

Pollution in eastern China cuts light, useful rainfall